Process for the reduction of acidic contaminates in fluorinated hydrocarbons

ABSTRACT

The present invention relates to processes for reducing the concentration of acidic impurities HF, HCl, HBr, HI, HNO 3  and H 2 SO 4  in fluorinated hydrocarbons. The process involves: (i) contacting the fluorinated hydrocarbon with a phosphorous oxyacid salt, and (ii) recovering the fluorinated hydrocarbon having reduced concentration of, or substantially free of, said acidic contaminant, provided that said fluorinated hydrocarbon is not CF 3 CH 2 CF 3  or CF 3 CHFCF 3 .

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for reducing theconcentration of acidic contaminates in fluorinated hydrocarbons bycontact with a phosphorous oxyacid salt.

2. Description of Related Art

Chlorine- and bromine-substituted fluorinated hydrocarbons have longfound applications as refrigerants, blowing agents, propellants,solvents, and fire extinguishants. However, dissociation of thesematerials in the atmosphere has been linked to depletion ofstratospheric ozone. Many of these materials have been replaced byfluorinated hydrocarbons that contain only carbon, hydrogen, andfluorine (i.e., hydrofluorocarbons or HFC's). Examples of suchhydrofluorocarbons include 1,1,1,2,3,3,3-heptafluoropropane (CF₃CHFCF₃or HFC-227ea, an aerosol propellant and fire extinguishant),1,1,1,3,3,3-hexafluoropropane (CF₃CH₂CF₃ or HFC-236fa, a fireextinguishant and refrigerant), 1,1,1,3,3-pentafluoropropane (CF₃CH₂CHF₂or HFC-245fa, a polymer foam blowing agent), and1,1,1,2-tetrafluoroethane (CF₃CH₂F or HFC-134a, a refrigerant andaerosol propellant).

Commercial manufacturing processes for hydrofluorocarbons often involveaddition of HF, an inorganic acid, to olefins. For example, HFC-227ea isprepared by addition of HF to hexafluoropropene (see U.S. Pat. No.6,281,395). Other processes involve reacting HF with chlorinatedhydrocarbons such as chloroolefins, chloroalkanes, or partiallyfluorinated chlorocarbons. For example, HFC-236fa is prepared byreacting HF with 1,1,1,3,3,3-hexachloropropane and HFC-245fa is preparedby reacting HF with 1,1,1,3,3-pentachloropropane (see U.S. Pat. No.6,291,730). In this type of exchange process, HCl, an inorganic acid, isformed as a by-product of the substitution of fluorine for chlorine.Other hydrofluorocarbon manufacturing processes involve replacement of achlorine substituent in a chlorofluorocarbon or ahydrochlorofluorocarbon with a hydrogen substituent by reaction withhydrogen with elimination of HCl. For example, HFC-134a is prepared byreaction of hydrogen with 1,1-dichloro-1,2,2,2-tetrafluoroethane (seeU.S. Pat. No. 5,208,397) and HFC-236fa is prepared by reaction ofhydrogen with 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane (seeInternational Patent Application No. 96/17,813).

Fluoroolefins such as hexafluoropropene (C₃F₆, HFP) and1,1,3,3,3-pentafluoro-1-propene (CF₃CH═CF₂, HFC-1225zc) are anotherclass of fluorinated hydrocarbons of commercial interest; thesecompounds are often useful as polymer intermediates. Fluoroolefins maybe prepared under conditions where acidic contaminants may be present.For example, U.S. Pat. No. 5,057,634 discloses a process for preparationof hexafluoropropene comprising as a final step hydrodehalogenatingCF₃CClFCF₃ in the presence of hydrogen and a catalyst. U.S. Pat. No.6,093,859 discloses a process for producing HFC-1225zc involvingdehydrofluorinating HFC-236fa at an elevated temperature in the vaporphase over a catalyst.

The crude product in the aforementioned processes may be contaminatedwith hydrogen chloride (HCl) and/or hydrogen fluoride (HF). Removal ofHCl and HF is usually accomplished by distillation, but traces of theseacidic contaminants often remain in the product. Even afterdistillation, fluorinated hydrocarbons may remain contaminated with HFor HCl due to the formation of azeotropes or azeotrope-likecompositions; that is constant-boiling mixtures that behave as a singlesubstance. For example, it has been disclosed that HFC-227ea forms anazeotrope with HF (see U.S. Pat. No. 6,376,272) and HFC-236fa forms anazeotrope with HF (see U.S. Pat. No. 5,563,304). These acidiccontaminants must be removed from the hydrofluorocarbons prior tocommercial use.

It is well-known that acidic contaminants in perhalogenatedfluorocarbons (e.g., CCl₂F₂) may be removed by treatment with a strongbase such as sodium hydroxide without degradation of the perhalogenatedfluorocarbon. However, substitution of one or more hydrogen substituentsin a saturated hydrocarbon by a halogen (i.e., fluorine, chlorine,bromine, or iodine) often increases the acidity of at least some of theremaining hydrogen substituents (see the discussion by Reutov,Beletskaya, and Butin on pages 51 to 58 in CH-Acids, Pergamon Press,Oxford, (1978)). Depending on the particular arrangement of hydrogen andhalogen substituents, exposure of a saturated partially halogenatedhydrocarbon to a base such as sodium hydroxide may result in facileelimination of the corresponding hydrogen halide from the halogenatedhydrocarbon by dehydrohalogenation, which is the elimination of hydrogenhalide from a saturated halogenated hydrocarbon to produce anunsaturated halogenated compound. The unsaturated compound so formed canbe acyclic (linear or branched) or cyclic, depending upon the startinghalogenated hydrocarbon.

Therefore, removal of acidic contaminants from saturated halogenatedhydrocarbons by contacting mixtures of saturated halogenatedhydrocarbons and HF or HCl with strong bases, such as sodium hydroxide,potassium hydroxide, sodium carbonate, or potassium carbonate, mayresult in the formation of substantial amounts of unsaturated compounds(e.g., amounts greater than 5 weight per cent of the startinghalogenated hydrocarbon) due to elimination of hydrogen halide throughdehydrohalogenation. For example, as disclosed in the examples herein,contact of HFC-227ea with strong base gives some hexafluoropropene,contact of HFC-236fa with strong base gives some1,1,3,3,3-pentafluoro-1-propene, contact of HFC-245fa with strong basegives some 1,3,3,3-tetrafluoro-1-propene, contact of2,3-dichloro-1,1,1,3,3,3-pentafluoropropane (CF₃CHClCClF₂, HCFC-225da)with strong base gives some 2-chloro-1,1,3,3,3-pentafluoro-1-propene,and contact of 1,1,1,2,2,3,4,5,5,5-decafluoropentane (CF₃CF₂CHFCHFCF₃,HFC-43-10mee) with strong base gives some nonafluoropentenes.

U.S. Pat. No. 6,187,976 example 5 discloses a liquid phase fluorinationprocess for CCl₃CH₂CCl₃. The product stream consisting of HCFC-235fa(1-chloro-1,1,3,3,3-pentafluoropropane), HFC-236fa(1,1,1,3,3,3-hexafluoropropane), 1,1,3,3,3-pentafluoropropene, HF, HCl,and other minor products is passed through a caustic scrubber. Theacid-free product stream contains 25% 1,1,3,3,3-pentafluoropropene.

Because unsaturated fluorocarbons are frequently toxic, their presencein a hydrofluorocarbon product is undesirable. Removal of suchunsaturated compounds by distillation is often difficult due to the factthat they may have boiling points close to those of thehydrofluorocarbons or they may even form azeotropes or azeotrope-likemixtures with the hydrofluorocarbons. Thus, formation of unsaturatedimpurities during a neutralization process is not only a yield loss, butresults in the need for additional purification steps which add to theoverall cost of the manufacturing process.

Highly fluorinated olefins such as HFP and HFC-1225zc are well-known tobe reactive toward nucleophiles (e.g., the anionic portion of a compoundsuch as sodium hydroxide where the hydroxide ion is the nucleophile).Therefore, removal of acidic contaminants from highly fluorinatedolefins by contacting mixtures of highly fluorinated olefins and HF orHCl with strong bases, such as sodium hydroxide, potassium hydroxide,sodium carbonate, or potassium carbonate, may result in nucleophilicattack by hydroxide ion at the double bond with hydrolysis (i.e.,replacement of the fluoride ion by hydroxide ion) of the olefin andformation of fluoride ions. This can result in a substantial yield loss,such as a yield loss of greater than 5 weight percent of the startingfluorinated olefin. World Intellectual Property Organization patentapplication publication no. WO 96/29,296 discloses a method forproducing fluoroalkanes by high-temperature pyrolysis ofchlorodifluoromethane in the presence of an alkane or fluoroalkane. Theproducts of said process are scrubbed with caustic soda prior toisolation (page 3, lines 3, 4, and 5); little fluoroolefins are observedin the products and apparently about 40% of the yield is not to usefulproducts.

There is an industry need for a process to remove acidic contaminationfrom saturated and unsaturated fluorinated hydrocarbons in which thedehydrohalogenation of saturated fluorinated hydrocarbons or hydrolysisof unsaturated fluorinated hydrocarbons is reduced. The presentinvention meets that need.

BRIEF SUMMARY OF THE INVENTION

The present invention is a process for reducing the concentration ofacidic contaminates HF, HCl, HBr, HI, HNO₃ and H₂SO₄ in fluorinatedhydrocarbons and involves the steps of: (i) contacting the fluorinatedhydrocarbon with a phosphorous oxyacid salt such as orthophosphoric acidsalts, phosphorous acid salts, metaphosphoric acid salts, andpyrophosphoric acid salts, and (ii) recovering the fluorinatedhydrocarbon having reduced concentration of, or substantially free of,said acidic contaminant, provided that said fluorinated hydrocarbon isnot CF₃CH₂CF₃ or CF₃CHFCF₃. The contacting step of the present processis preferably carried out with the phosphorous oxyacid salt in aqueoussolution having a pH of no more than about 10. The present processresults in less than about 5 weight percent of the fluorinatedhydrocarbon being decomposed by dehydrohalogenation or by hydrolysisduring the contacting step and is an improvement over prior artprocesses for removing such acidic impurities from fluorinatedhydrocarbons.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides a process for reducing the amount of acidiccontaminants from fluorinated hydrocarbons by contactingacid-contaminated fluorinated hydrocarbons with phosphorous oxyacidsalts.

As is well known in the art, when acidic contaminants are contacted withphosphorous oxyacid salts, the acidic contaminant is converted to thecorresponding salt. The present inventors have found that when saidcontacting of the acidic contaminant with the phosphorous oxyacid saltsis carried out in the presence of cyclic or acyclic, saturated orunsaturated fluorinated hydrocarbons, reduction or substantial removalof the quantity of acidic contaminant occurs without substantialdehydrohalogenation of the saturated fluorinated hydrocarbon orhydrolysis of the unsaturated fluorinated hydrocarbon. By “withoutsubstantial dehydrohalogenation of the saturated fluorinatedhydrocarbon” is meant that less than about 5 weight percent of thesaturated fluorinated hydrocarbon is converted to an unsaturatedfluorinated hydrocarbon. Preferably, less than about 0.5 weight percentof the saturated fluorinated hydrocarbon is converted to an unsaturatedfluorinated hydrocarbon. By “without substantial hydrolysis of theunsaturated fluorinated hydrocarbon” is meant that less than about 5weight percent of the unsaturated fluorinated hydrocarbon is convertedto other products by hydrolysis. Preferably, less than about 0.5 weightpercent of the unsaturated fluorinated hydrocarbon is converted to otherproducts by hydrolysis. By “substantial removal” or “substantially free”means that the present process produces a fluorinated hydrocarbonproduct containing 10 ppm-molar or less, preferably 1 ppm-molar or less,of acidic contaminants.

Phosphorous oxyacid salts of the present invention are: (i)orthophosphoric acid salts of the formula M_(n)H_(3-n)PO₄, wherein n isan integer from 1 to 3; (ii) phosphorous acid salts of the formulaM_(m)H_(2-m)(HPO₃), wherein m is 1 or 2; (iii) metaphosphoric acid saltsof the formula (MPO₃)_(z), wherein z is an integer from 1 to 6; and (iv)pyrophosphoric acid salts of the formula M_(k)H_(4-k)P₂O₇, wherein k isan integer from 1 to 4; wherein M is selected from the group consistingof NH₄, Li, Na, and K. Preferred phosphorous oxyacid salts of thepresent invention are orthophosphoric acid salts of the formulaM_(n)H_(3-n)PO₄, wherein n is an integer from 1 to 3, and M is selectedfrom the group consisting of NH₄, Na, and K. Owing to their availabilityand favorable solubility in water, mixtures of the potassium salts oforthophosphoric acid (K₃PO₄, K₂HPO₄, and KH₂PO₄) are the most preferredphosphorous oxyacid salts. Example salts of orthophosphoric acid includetribasic sodium phosphate (Na₃PO₄), dibasic sodium phosphate (Na₂HPO₄),monobasic sodium phosphate (NaH₂PO₄), tribasic potassium phosphate(K₃PO₄), dibasic potassium phosphate (K₂HPO₄), monobasic potassiumphosphate (KH₂PO₄), dibasic ammonium phosphate ((NH₄)₂HPO₄), monobasicammonium phosphate (NH₄H₂PO₄), tribasic lithium phosphate (Li₃PO₄),dibasic lithium phosphate (Li₂HPO₄), monobasic lithium phosphate(LiH₂PO₄), and their various hydrated salts. Other suitable saltsinclude mixed salts such as for example, sodium ammonium hydrogenphosphate (NH₄NaHPO₄). Example salts of pyrophosphoric acid suitableinclude potassium pyrophosphate (K₄P₂O₇) or sodium pyrophosphate(Na₄P₂O₇) or their mixtures with pyrophosphoric acid. Example salts ofmetaphosphoric acid include “sodium polyphosphate” (NaPO₃)_(p) or itsmixtures with metaphosphoric acid.

Mixtures of any of the aforementioned phosphorous oxyacid salts may alsofind utility in the present process.

The contacting step of the present invention may be carried out bypassing a gaseous or liquid mixture of fluorinated hydrocarbon(s) andacidic contaminant(s) through a bed of substantially dry phosphorousoxyacid salt(s). The salt is consumed in the contacting step and ispreferably finely divided to ensure intimate contact with the mixture.In this embodiment, the mixture may be vaporized alone or in combinationwith an inert carrier gas such as nitrogen. Stirring and agitation ofthe bed may be carried out through use of known methods.

The contacting step of the present invention may also, and morepreferably, be carried out by contacting a gaseous or liquid mixture offluorinated hydrocarbon(s) and acidic contaminant(s) with an aqueoussolution of phosphorous oxyacid salt(s). The concentration ofphosphorous oxyacid salts in said aqueous solutions is not critical andis typically from about 1 percent by weight to about 20 percent byweight, preferably from about 3 percent by weight to about 10 percent byweight. Lower concentrations of salts may be volumetrically inefficientin removal of acid contaminants and higher concentrations may tend toform precipitates.

Said aqueous solutions may be prepared by adding the desiredquantity(ies) of phosphorous oxyacid salt(s) to water, by adding thedesired quantity of a base such as an alkali metal hydroxide to asolution of the phosphorous oxyacid, by adding the desired quantity ofphosphorous oxyacid to a solution of alkali metal hydroxide, or bymixing a phosphorous oxyacid with one or more phosphorous oxyacid salts.Other bases, such as ammonia, may be used to neutralize the phosphorousoxyacid.

Preferred aqueous solutions of phosphorous oxyacid salts used in theprocess of the present invention may have a pH in the range of fromabout 6 to about 10. Fluorinated hydrocarbons having relatively acidichydrogen substituents, that is those having acidity constants (pK_(a))of about 25 or less, may require the use of basic aqueous solutionshaving a pH in the range of about 6 to about 8, while for less reactivefluorinated hydrocarbons, the pH of the aqueous solution may reach 10without formation of significant amounts of unsaturated by-products. Asillustrated in the present examples, use of aqueous solutions ofphosphorous oxyacid salts or other basic salts having a pH greater than10 may result in a significant conversion of a saturated fluorinatedhydrocarbon to an unsaturated compound, or in hydrolysis of anunsaturated fluorinated hydrocarbon. The formation of unsaturatedcompounds may be detected by analysis of the fluorinated hydrocarbon. Inaddition, the formation of unsaturated impurities from saturatedfluorinated hydrocarbons, as well as the hydrolysis of unsaturatedfluorinated hydrocarbons, is accompanied by the appearance of halideions (e.g., fluoride or chloride) in the recovered aqueous solutions.

Because phosphorous oxyacid salts form buffer solutions, the use ofthese materials for the process of this invention in the preferred pHrange is advantageous compared with use of highly basic compounds (suchas sodium hydroxide or potassium hydroxide) in the same pH range,because a high degree of pH monitoring is not necessary.

Acidic contaminants that may be removed from fluorinated hydrocarbons ofthis invention are the inorganic acids HF, HCl, HBr, HI, HNO₃ and H₂SO₄.The present process is especially useful for reducing or removing theacidic contaminants HF and HCl, which are often otherwise difficult toremove from fluorinated hydrocarbons. These contaminants arise fromprevious processing steps which involve these acids directly or asby-products such as in reactions with HF (fluorination), chlorine and HF(chlorofluorination), chlorine (chlorination), bromine (bromination),hydrogen (such as hydrodechlorination or hydrodefluorination), or withsulfuric acid (such as in HF recovery).

Saturated acyclic fluorinated hydrocarbons of the present invention arecompounds represented by the formula C_(a)H_(b)F_(c)W_(d)R_(e), whereina is an integer from 1 to 10, b is an integer at least 1, c is aninteger at least 1, d is an integer from 0 to 10, e is an integer from 0to 4, the sum of b, c, d, and e is equal to 2a+2, and wherein: W isselected from the group consisting of Cl, Br, and I; R is functionalgroup selected from the group consisting of aryl, C₁-C₁₂ alkyl, C₁-C₁₂polyhaloalkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ polyhaloalkenyl, C₂-C₁₂ alkynyl,C₃-C₁₂ polyhaloalkynyl, C(O)R¹, CO₂R¹, C(O)H, CN, NO₂, OR¹, O₂CR¹, andSO₂R¹; and R¹ is aryl, C₁-C₆ alkyl, and C₁-C₆ polyhaloalkyl.

Saturated cyclic fluorinated hydrocarbons of the present invention arecompounds represented by the formula C_(f)H_(g)F_(h)W_(i)R_(j), whereinf is an integer from 3 to 6, g is an integer at least 1, h is an integerat least 1, i is an integer from 0 to 10, j is an integer from 0 to 4,the sum of g, h, i, and j is equal to 2f, and W and R are as definedearlier herein for the present saturated acyclic fluorinatedhydrocarbons.

Unsaturated acyclic fluorinated hydrocarbons of the present inventionare compounds represented by the formula C_(n)H_(p)F_(q)W_(r)R_(s),wherein n is an integer from 2 to 6, p is an integer from 0 to 11, q isan integer at least 1, r is an integer from 0 to 8, s is an integer from0 to 4, the sum of p, q, r, and s is equal to 2n, and W and R are asdefined earlier herein for the present saturated acyclic fluorinatedhydrocarbons.

Unsaturated cyclic fluorinated hydrocarbons of the present invention arecompounds represented by the formula C_(t)H_(u)F_(v)W_(x)R_(y), whereint is an integer from 3 to 6, u is an integer from 0 to 9, v is aninteger at least 1, x is an integer from 0 to 8, and y is an integerfrom 0 to 4, the sum of u, v, x, and y is equal to 2t-2, and where W andR are as defined earlier herein for the present saturated acyclicfluorinated hydrocarbons.

More preferably, the process of the present invention is carried outwherein said at least one fluorinated hydrocarbon is selected from thegroup consisting of: (i) saturated acyclic fluorinated hydrocarbons ofthe formula C_(a)H_(b)F_(c), wherein a is an integer from 1 to 10, b isan integer from 1 to 21, c is an integer from 1 to 21, and the sum of band c is equal to 2a+2, (ii) saturated cyclic fluorinated hydrocarbonsof the formula C_(f)H_(g)F_(h), wherein f is an integer from 3 to 6, gis an integer from 1 to 11, h is an integer from 1 to 11, and the sum ofg and h is equal to 2f, (iii) unsaturated acyclic fluorinatedhydrocarbons of the formula C_(n)H_(p)F_(q), wherein n is an integerfrom 2 to 6, p is an integer from 0 to 11, q is an integer from 1 to 12,and the sum of p and q is equal to 2n, and (iv) unsaturated cyclicfluorinated hydrocarbons of the formula C_(t)H_(u)F_(v), wherein t is aninteger from 3 to 6, u is an integer from 0 to 9, v is an integer from 1to 10, and the sum of u and v is equal to 2t-2.

The present inventive process is especially suitable for saturated,acyclic or cyclic, fluorinated hydrocarbons having relatively acidichydrogen substituents. The acidity of the hydrogen substituents isinfluenced by the presence of electron-withdrawing substitutents, suchas halogens or polyhaloalkyl groups such as CF₃, in the molecule. Suchcompounds are characterized by pK_(a) values in the range of from about11 to about 25 as discussed by Smart on pages 988 to 989 of Chemistry ofOrganic Fluorine Compounds II, edited by M. Hudlicky and A. E. Pavlath,ACS Monograph 187, American Chemical Society, Washington, D.C. (1995),and by Reutov, Beletskaya, and Butin on pages 51 to 58 in CH-Acids,Pergamon Press, Oxford (1978). These compounds are also characterized byhalogen substitution patterns which have vicinal hydrogen and halogensubstitutents that allow the possibility of facile elimination ofhydrogen halide in the presence of a strong base. Examples ofsubstitution patterns that promote easy elimination of hydrogen halidein the presence of strong base include acyclic and cyclic compoundshaving the following structural features: —CHZCHZ—, —CZ₂CHZ—, —CH₂CHZ—,—CZ₂CH₂—, CZ₃CHZ—, and CZ₃CH₂—where Z is independently selected from thegroup consisting of F, Cl, Br, and I. In particular, compounds such asHFC-236fa, HCFC-235fa (CF₃CH₂CClF₂), and HFC-245fa which have thestructural feature —CZ₂CH₂CZ₂—, are surprisingly reactive toward aqueoussolutions having a pH greater than about 10.

Representative saturated acyclic fluorinated hydrocarbons of the presentinvention, compounds that are relatively acidic and susceptible toelimination of HF include, but are not limited to,1,1,1,2,3,3,3-heptafluoropropane (CF₃CHFCF₃, HFC-227ea),1,1,1,3,3,3-hexafluoropropane (CF₃CH₂CF₃, HFC-236fa),1,1,1,2,3,3-hexafluoropropane (CF₃CHFCHF₂, HFC-236ea),1,1,1,3,3-pentafluoropropane (CF₃CH₂CHF₂, HFC-245fa),1,1,1,2,3-pentafluoropropane (CF₃CHFCH₂F, HFC-245eb),1,1,2,3,3-pentafluoropropane (CHF₂CHFCHF₂, HFC-245ea),1,1,1,3-tetrafluoropropane (CF₃CH₂CH₂F, HFC-254fb),1,1,1,3,3,3-hexafluoro-2-trifluoromethylpropane ((CF₃)₃CH, HFC-356mz),1,1,1,2,2,4,4,4-octafluorobutane (CF₃CF₂CH₂CF₃, HFC-338mf),1,1,1,3,3-pentafluorobutane (CH₃CF₂CH₂CF₃, HFC-365mfc),1,1,1,2,2,3,4,5,5,5-decafluoropentane (CF₃CHFCHFCF₂CF₃, HFC-43-10mee),1,1,1,2,2,4,4,5,5,5-decafluoropentane (CF₃CF₂CH₂CF₂CF₃, HFC-43-10mcf),1,1,1,2,2,3,3,5,5,5-decafluoropentane (CF₃CH₂CF₂CF₂CF₃, HFC-43-10mf),and 1,1,1,2,2,3,4,5,5,6,6,7,7,7-tridecafluoroheptane(CF₃CF₂CHFCHFCF₂CF₂CF₃, HFC-63-14mcee). Representative saturated cyclicfluorinated hydrocarbons of the present invention, compounds that arerelatively acidic and susceptible to elimination of HF include, but arenot limited to, 1,1,2,2,3,3,4,4,5-nonafluorocyclopentane(cyclo-CHFCF₂CF₂CF₂CF₂—), 1,1,2,2,3,3,4,5-octafluorocyclopentane(cyclo-CHFCHFCF₂CF₂CF₂—), 1,1,2,2,3,3,4-heptafluorocyclopentane(cyclo-CH₂CHFCF₂CF₂CF₂—).

Representative examples of saturated acyclic fluorinated hydrocarbons ofthe present invention substituted with other halogens or functionalgroups which are relatively acidic and susceptible to elimination of HY(hydrogen halide) include, but are not limited to,1,1,2-trichloro-2,2-difluoroethane (CHCl₂CClF₂, HCFC-122),2,2-dichloro-1,1,1-trifluoroethane (CHCl₂CF₃, HCFC-123),2,3-dichloro-1,1,1,3,3-pentafluoropropane (CF₃CHClCClF₂, HCFC-225da),2-chloro-1,1,1,3,3,3-hexafluoropropane (CF₃CHClCF₃, HCFC-226da),3-chloro-1,1,1,2,3,3-hexafluoropropane (CF₃CHFCClF₂, HCFC-226ea),2,3,3-trichloro-1,1,1-trifluoropropane (CF₃CHClCHCl₂, HCFC-233da),2,3-dichloro-1,1,1,3-tetrafluoropropane (CF₃CHClCHClF, HCFC-234da),3-chloro-1,1,1,3,3-pentafluoropropane (CF₃CH₂CClF₂, HCFC-235fa),2-chloro-1,1,1,3,3-pentafluoropropane (CF₃CHClCHF₂, HCFC-235da),2,3-dichloro-1,1,1-trifluoropropane (CF₃CHClCH₂Cl, HCFC-243db),3-chloro-1,1,1,3-tetrafluoropropane (CF₃CH₂CHClF, HCFC-244fa),2,3-dibromo-1,1,1,3,3-pentafluoropropane (CF₃CHBrCBrF₂),2,3-dibromo-1,1,1-trifluoropropane (CF₃CHBrCH₂Br),2,3-dibromo-1,1,1,3-tetrafluoropropane (CF₃CHBrCHBrF),1,1,1,2,3,3-hexafluoro-3-methoxypropane (CF₃CHFCF₂OCH₃),1,1,1,2-tetrafluoro-2-methoxyethane (CF₃CHFOCH₃),1,1,2-trifluoro-1-methoxy-2-trifluoromethoxyethane (CH₃OCF₂CHFOCF₃),1,1,1-trifluoro-2-difluoromethoxyethane (CF₃CH₂OCHF₂),1,1,1-trifluoro-2-trifluoromethoxyethane (CF₃CH₂OCF₃),1,1,1,2-tetrafluoro-2-trifluoromethoxyethane (CF₃CHFOCF₃),1,1,1,2-tetrafluoro-2-difluoromethoxyethane (CF₃CHFOCHF₂),2,3,3,3-tetrafluoropropionitrile (CF₃CHFCN), and methyl3,3,3-trifluoropropionate (CF₃CHFCO₂CH₃).

Representative acyclic and cyclic unsaturated fluorinated compounds ofthe present invention, compounds that can undergo nucleophilic attackand/or hydrolysis, include tetrafluoroethylene (CF₂═CF₂, TFE),hexafluoropropene (CF₃CF═CF₂, HFP), 1,1,3,3,3-pentafluoro-1-propene(CF₃CH═CF₂, HFC-1225zc), 1,1,2,3,3-pentafluoro-1-propene (CHF₂CF═CF₂,HFC-1225yc), 2-chloro-1,1,3,3,3-pentafluoro-1-propene (CF₃CCl═CF₂,CFC-1215xc), and hexafluorocyclobutene (cyclo-C₄F₆).

The process of the present invention is also useful for reducing theconcentration of acidic contaminants from a mixture comprising saturatedand unsaturated fluorinated hydrocarbons without substantial degradationof said saturated and unsaturated fluorinated hydrocarbons. Examples ofmixtures of saturated hydrofluorocarbons and unsaturated fluorinatedhydrocarbons which may be treated to remove acidic contaminants by theprocess of this invention include, but are not limited to, mixtures ofHFC-227ea and HFP, mixtures of HFC-236fa and HFC-1225zc, mixtures ofHFC-236ea and HFC-1225ye, mixtures of HFC-245fa and HFC-1234ze(CF₃CH═CHF), mixtures of HFC-227ea, HFC-236fa, HFP, and HFC-1225zc,mixtures of HFC-227ea, HFC-245fa, HFP, and HFC-1234ze, and mixtures ofHFC-236fa, HFC-245fa, HFC-1234ze, and HFC-1225zc.

The present invention is also suitable for removing acidic contaminantsfrom mixtures of saturated and/or unsaturated fluorinated hydrocarbonsin which the acidic contaminants are present as an azeotrope with one ormore of the fluorinated hydrocarbons. Examples of azeotropes ofinorganic acids and fluorinated hydrocarbons which may be treated toremove the acidic contaminant by the process of this invention include,but are not limited to, the HF azeotrope of HFC-227ea as described inU.S. Pat. No. 6,376,727, the HF azeotrope of HFC-236ea as described inU.S. Pat. No. 5,563,304, the HF azeotrope of HFC-236fa as described inU.S. Pat. No. 5,563,304, the HF azeotrope of HCFC-235fa as described inU.S. Pat. No. 6,291,730, and the HF azeotrope of HFC-245fa as describedin U.S. Pat. No. 6,291,730.

The contacting step of the present invention in which a mixturecontaining one or more fluorinated hydrocarbons and one or more acidiccontaminants is contacted with an aqueous solution of salts ofphosphorous oxyacids may be accomplished by any one of several methodsusing well-known chemical engineering practices for scrubbing organiccompounds. This step may be carried out in batch or continuous mode. Inone embodiment of the invention, the mixture containing theacid-contaminated fluorinated hydrocarbon may be contacted with theaqueous solution under a suitable amount of pressure to maintain aliquid phase of the fluorinated hydrocarbon in the contacting vessel.The contents of the vessel may be agitated to provide contact betweenthe aqueous solution and the fluorinated hydrocarbon. The fluorinatedhydrocarbon is then collected as a lower layer from the vessel orrecovered by distillation.

In another embodiment of the present process, the mixture containing theacid-contaminated fluorinated hydrocarbon may be bubbled into theaqueous solution as a gas in a stirred tank reactor. The fluorinatedhydrocarbon is then allowed to leave the reactor, optionally through acondenser, where it is collected for subsequent purification.

In a preferred embodiment of the present invention, the contacting stepis conducted in a column packed with materials such as helices, rings,saddles, spheres or other formed shapes fabricated from glass, plastic,or ceramics. The mixture of fluorinated hydrocarbon(s) and acidiccontaminant(s) enters the bottom of the column as a vapor. The aqueoussolution enters the top of the column, for example, by means of a pumpconnected to a reservoir of said aqueous solution. The acidiccontaminant(s) in the fluorinated hydrocarbon then reacts with theaqueous solution in the column and the fluorinated hydrocarbon vapor,with reduced acidic contaminant, passes out the top of the column and isthen collected. The aqueous solution passes out the bottom of the columnand returns to the reservoir.

The aqueous solution may be used until its pH drops to a pre-determinedpoint typically from about 6 to about 7. The aqueous solution is thenreplaced or treated with additional base, such as potassium hydroxide,to bring the pH to the desired value. The restoration of the pH maycontinue until the concentration of salts in the aqueous solutionreaches the desired value, usually not to exceed about 20 weightpercent.

The pressure during the contacting steps is not critical, thoughatmospheric and superatmospheric pressures are preferred. Operating theprocess under pressure may be advantageous for subsequent purificationsteps such as distillations.

The temperature during the contacting step of the mixture containing thefluorinated hydrocarbon(s) and acidic contaminant(s) with the aqueoussolution of phosphorous oxyacid salts is not critical and may take placeat temperatures of from about 0° C. to about 100° C., preferably fromabout 25° C. to about 80° C. Lower temperatures than about 25° C. mayresult in loss of fluorinated hydrocarbon due to condensation or tosolubility in the aqueous phase. Temperatures higher than about 80° C.increase the rate of undesirable elimination processes as observed byincreased levels of unsaturated impurities in the fluorinatedhydrocarbon and increased levels of halide ion (e.g., fluoride) in theaqueous phase.

The time of contact between the mixture of the fluorinated hydrocarbonand the aqueous solution is not critical and typically may be on theorder of about 30 seconds to about an hour. In the preferred embodimentof the invention, the contact time may be typically from about 30seconds to about 10 minutes.

In the recovering step of the process of the present invention,fluorinated hydrocarbon product(s) that has been freed of the acidcontaminant(s) is delivered to a separation unit for recovery. Thefluorinated hydrocarbon product will typically be separated from waterby means of a decanter, by distillation, or by drying with a molecularsieve or anhydrous salt (for example, calcium sulfate), or by acombination thereof. The fluorinated hydrocarbon product may then befurther purified by distillation.

Without further elaboration, it is believed that one skilled in the artcan, using the description herein, utilize the present invention to itsfullest extent. The following specific embodiments are, therefore, to beconstrued as merely illustrative, and do not constrain the remainder ofthe disclosure in any way whatsoever.

EXAMPLES

LEGEND 123 is CF₃CHCl₂ 225da is CF₃CHClCClF₂ 227ea is CF₃CHFCF₃ 235fa isCF₃CH₂CClF₂ 236ea is CF₃CHFCHF₂ 236fa is CF₃CH₂CF₃ 245fa is CF₃CH₂CHF₂365mfc is CF₃CH₂CF₂CH₃ 43-10mee is CF₃CHFCHFCF₂CF₃ 1225zc is CF₃CH═CF₂HFP is CF₃CF═CF₂Preparation of Solutions of Aqueous Bases

Preparation of 6.5:1 Na₂HPO₄/NaH₂PO₄ Solutions

A 20 wt % stock solution of 6.5:1 Na₂HPO₄/NaH₂PO₄ (mole basis) wasprepared by adding 14.90 g (0.09552 mole) NaH₂PO₄[2(H₂O)] and 88.55 g(0.6238 mole) Na₂HPO₄ to a flask and bringing the total weight to 500.0g with deionized water. The solution was 2.29 wt % NaH₂PO₄ (based on theanhydrous salt) and 17.71 wt % Na₂HPO₄. The 20% buffer stock solutionprepared above was then diluted 1 to 5 by weight with water to give a 4wt % buffer solution (3.54 wt % Na₂HPO₄, 0.458 wt % NaH₂PO₄) having a pHof 7.54.

Preparation of 5.7:1 K HPO₄/KH₂PO₄ Solutions

136.4 g (1.193 mole) of H₃PO₄ (85.7%) was diluted with 400.7 g of waterin a large Erlenmeyer flask. The resulting acid solution was treateddropwise with 412.9 g (2.208 mole) of 30 wt % KOH (prepared bydissolving 171.8 g of 87.3% KOH pellets in 328.2 g of DI water). Theaddition funnel was rinsed into the final solution with an additional50.0 g of water. The resulting solution is about 17.7 wt % K₂HPO₄ and2.4 wt % KH₂PO₄. A 4 wt % potassium phosphate buffer solution wasprepared by diluting the 20 wt % buffer 1 to 5 with water; the pH of thesolution was 7.43.

Preparation of 6:1 K₂HPO₄/KH₂PO₄ Solutions

17.70 g (0.102 mole) of K₂HPO₄ and 2.30 g (0.0169 mole) of KH₂PO₄ weredissolved in water and brought to a total weight of 100 g. The resultingsolution was diluted 1 to 5 with water to give a 4% (w/w) solutionhaving a pH of 7.92.

Preparation of 98:2 K₂HPO₄/K₃PO₄ Solutions

19.515 g (0.112 mole) of K₂HPO₄ and 0.485 g (0.00228 mole) of K₃PO₄ weredissolved in water and brought to a total weight of 100 g. The resultingsolution was diluted 1 to 5 with water to give a 4% (w/w) solutionhaving a pH of 9.93.

Preparation of 1:1 K₂HPO₄/K₃PO₄ Solutions

9.015 g (0.0518 mole) of K₂HPO₄ and 10.985 g (0.0517 mole) of K₃PO₄ weredissolved in water and brought to a total weight of 100 g. The resultingsolution was diluted 1 to 5 with water to give a 4% (w/w) solutionhaving a pH of 11.86.

Preparation of 6% Na₂CO₃/3% Na₂SO₃ Solution

10.5 g (0.0991 mole) of Na₂CO₃ and 5.25 g (0.0417 mole) of Na₂SO₃ weredissolved in water (159.25 g). The pH of the resulting solution was11.63.

Preparation of 2% Na₂CO₃ Solution

3.5 g (0.0330 mole) of Na₂CO₃ were dissolved in water (171.5 g). The pHof the resulting solution was 11.49.

Preparation of 2% Na₂SO₃ Solution

3.5 g (0.0278 mole) of Na₂SO₃ were dissolved in water (171.5 g). The pHof the resulting solution was 10.04.

General Procedure for Assessing Reactivity of Hydrofluorocarbons withBasic Aqueous Solutions

The reactivity of various hydrofluorocarbons with bases was assessed bycontacting a mixture of the two in sealed tubes (shaker tubes) or in acounter-current scrubber at a specified temperature for a specifiedperiod of time. The recovered hydrofluorocarbon was analyzed by GC. Therecovered aqueous phases was weighed, purged with nitrogen to expel anydissolved hydrofluorocarbon, and the pH determined. The chloride ionconcentration in the aqueous phase was determined by means of ionselective electrode. The fluoride ion concentration in the aqueous phasewas determined by means of an ion selective electrode or ionchromatography using authentic fluoride standards to calibrate themethods. Time average rates of decomposition of the fluorocarbons werebased on the concentrations of fluoride in the aqueous phase and thetime of agitation of the shaker tube or the time of fluorinatedhydrocarbon gas flow through the counter-current scrubber.

General Procedure for Shaker Tube Tests

A 400 mL stainless steel shaker tube was charged with 175.0 g of aqueousbase. The shaker tube was sealed, cooled in dry ice, evacuated, andpurged with nitrogen. The tube was re-evacuated and charged with 25.0 gof hydrofluorocarbon. The tube was then placed in the shaker mechanismand brought to the desired temperature with agitation. It generally took1-1.5 hours to bring the cold tube to the temperature set point. Thetube was then held at the desired temperature (either 40° C. or 100° C.)for 0.5 hour. After 0.5 hour, agitation was ceased and the tube wascooled in a stream of air. It typically took at least 0.5 hour to coolthe tube. If the hydrofluorocarbon was a gas at room temperature, it wascollected in an evacuated 300 mL cylinder chilled in dry ice. If thehydrofluorocarbon was a liquid at room temperature, it was dischargedwith the aqueous phase from the shaker tube and then separated as aliquid.

The results of contacting several fluorinated hydrocarbons with basicsolutions in shaker tubes are given in Table 1. “C” (e.g., C1) examplenumbers are comparative examples.

General Procedure for Counter-current Scrubber Tests

The counter-current scrubber consisted of an 46 cm×2.5 cm i.d. Pyrex™glass tube packed with 7×7 mm Raschig rings connected to a 5L flaskwhich served as a reservoir for the scrubbing medium. A variable speedperistaltic pump circulated the scrubbing solution from the reservoir tothe top of the column. The test gas entered the vapor space of thereservoir and moved up through the packed column where it contacted thebasic media. The scrubbed hydrofluorocarbon gas passed through a dryingtube packed with anhydrous calcium sulfate and condensed in a cylinderimmersed in dry ice.

The reservoir was charged with about 1 kg of scrubbing media. Thereactor system was purged with nitrogen at 100 sccm (1.7×10⁻⁶ m³/s) withthe pump feeding caustic at 100 mL/min while the temperature of thecaustic in the reservoir was brought to temperature (typically 60±2°C.). The nitrogen flow was then replaced with the fluorocarbon at a flowrate of 100 sccm (1.7×10⁻⁶ m³/s). Hydrofluorocarbon was fed to thescrubber for 2 to 3 hours; the pressure in the system was about twoinches of water (0.0049 atm). The hydrofluorocarbon flow was thenstopped and the system purged with nitrogen while the causticrecirculation rate was increased to about 400 mL/min. The contents ofthe reservoir were then discharged, weighed, the pH measured, andanalyzed for fluoride ion content. The hydrofluorocarbon recovered inthe collection cylinder was analyzed by GC-MS. The results of contactingHFC-236fa and HFC-245fa with basic solutions in a counter-currentscrubber are given in Table 2. “C” (e.g., C1) example numbers arecomparative examples.

TABLE 1 Alkaline Hydrolysis of Fluorinated Hydrocarbons in ShakerTubes^(a) Aqueous Average % % Unsaturates Example Temperature/ Phase^(e)ppm Aqueous Decomposition in Fluorinated No. Substrate^(b) ScrubbingMedia^(c) Time^(d) ° C./hours Cl Phase^(e) ppm F Per Hour^(f)Hydrocarbon^(g)  1 123   6% NaH₂PO₄ 50/8  7.7 0.5 0.0032 nd^(k) C1 123  6% Na₂CO₃/ 50/2  19200 <1000 33.1 15   3% Na₂SO₃ C2 123   6% KOH 50/2 28900 1500 49.8 86  2 225da   6% NaH₂PO₄ 50/8  116 8.6 0.057 0.3 C3225da   6% Na₂CO₃/ 50/2  22800 4300 47.6 94   3% Na₂SO₃ C4 225da   6%KOH 50/2  20000 4400 41.2 27  3 227ea 3.54% K₂HPO₄/  40/0.5 nd 2.00.025^(h) 0.0008 0.46% KH₂PO₄  4 227ea 3.54% K₂HPO₄/  100/0.5  nd 1.70.021^(h) 0.046 0.46% KH₂PO₄ C5 227ea   5% KOH  40/0.5 nd 49.1 0.61^(h)0.011 C6 227ea   5% KOH  100/0.5  nd 10440 21.9^(i) 0.29  5 235fa   6%NaH₂PO₄ 50/8  1.2 0.1 0.000041 0.06  6 235fa   4% KH₂PO₄  80/0.5 32 <0.50.21 nd C7 235fa   6% Na₂CO₃/ 25/4  833 700 0.68 0.12   3% Na₂SO₃ C8235fa   2% Na₂CO₃  40/0.5 1219 161 8.0 0.58 C9 235fa   2% Na₂SO₃  40/0.51066 102 7.0 0.34  7 236ea   6% NaH₂PO₄ 50/8  nd 0.1 0.000069 notmeasured  8 236ea 3.54% K₂HPO₄/  40/0.5 nd 0.75 0.0082 0.05 0.46% KH₂PO₄C10 236ea   6% Na₂CO₃/ 50/2  nd 52 0.14 not measured   3% Na₂SO₃ C11236ea   5% KOH  40/0.5 nd 625 6.87 3.  9 236fa   4% KH₂PO₄  80/0.5 2.0<0.5 0.0055^(h) 0.003 10 236fa   2% Na₂HPO₄/  80/0.5 14.0 <0.50.0055^(h) 0.0047   2% KH₂PO₂ C12 236fa   6% Na₂CO₃/ 25/4  nd 18.80.0043^(i) 0.023   3% Na₂SO₃ C13 236fa   6% Na₂CO₃/ 50/2  nd 71.90.033^(i) 0.085   3% Na₂SO₃ C14 236fa   2% Na₂CO₃  80/0.5 <5.0 5781.1^(i) 1.6 C15 236fa   5% KOH  40/0.5 nd 2330 4.3^(i) 0.4 11 245fa3.54% K₂HPO₄/  40/0.5 nd 1.4 0.0135 0.48 0.46% KH₂PO₄ 12 245fa 3.54%K₂HPO₄/  100/0.5  nd 37 0.357 0.63 0.46% KH₂PO₄ C16 245fa   5% KOH 40/0.5 nd 958 9.27 4.7 C17 245fa   5% KOH  100/0.5  nd 14752 145.7 7313 HFP 3.54% K₂HPO₄/  40/0.5 nd 9.1 0.049 nd 0.46% KH₂PO₄ 14 HFP 3.54%K₂HPO₄/  100/0.5  nd 854 4.64 nd 0.46% KH₂PO₄ C18 HFP   5% KOH  40/0.5nd 9640 54.8 nd C19 HFP   5% KOH  100/0.5  nd 8750 49.5 nd 15 1225zc  6% NaH₂PO₄ 50/8  63 2.5 0.00073^(h) nd 16 1225zc 3.54% K₂HPO₄/  40/0.5nd 9.0 0.043^(h) nd 0.46% KH₂PO₄ 17 1225zc 3.54% K₂HPO₄/  100/0.5  nd990 4.8^(h) nd 0.46% KH₂PO₄ C20 1225zc   6% Na₂CO₃/ 25/4  173 56501.4^(i) nd   3% Na₂SO₃ C21 1225zc   5% KOH  40/0.5 nd 9880 19.5^(i) nd18 365mfc 3.54% K₂HPO₄/  40/0.5 nd 13 0.14 j 0.46% KH₂PO₄ 19 365mfc3.54% K₂HPO₄/  100/0.5  nd 5 0.054 0.08 0.46% KH₂PO₄ C22 365mfc   5% KOH 40/0.5 nd 350 3.85 0.49 C23 365mfc   5% KOH  100/0.5  nd 14,130 158 5320 43-10mee 3.54% K₂HPO₄/  40/0.5 nd 8.0 0.15 0.015 0.46% KH₂PO₄ C2443-10mee   5% KOH  40/0.5 nd 5,000 91.4 46 ^(a)Reactions conducted in400 mL Hastelloy ™ C or stainless steel shaker tubes using 25.0 g offluorinated hydrocarbon and 175 g of aqueous scrubbing media. Blank runstypically contained 1.3 ppm chloride and 1 ppm fluoride.^(b)Fluorocarbon fed to scrubber; see Legend. ^(c)Type of aqueouscaustic solution used in shaker tube. Percentages are on a weight basis.^(d)Temperature in shaker tube during hold period and duration of holdperiod in hours. Typically took 1–1.5 hours to warm the shaker tube fromthe starting temperature of about −20° C. to the reaction temperature,and about 0.5 hour to cool the tube to ambient temperature after therun. ^(e)Concentration of halide in parts per million (weight) in therecovered aqueous phase at the end of the reaction period. ^(f)AverageRate of Decomposition per Hour = [(Halide concn.)(Wt. Aq.Soln)(100)]/[(f)(moles fluorocarbon)(At. Wt.)(Time, hours)] where Halideconcentration = ppm halide/1 × 10⁶; Wt. Aq. Soln = total weight ofaqueous phase recovered from tube f = stoichiometry factor; f = 6 for236fa and 227ea, f = 5 for 1225zc, f = 2 for HFP, f = 3 for 226da, f = 1for all other fluorocarbons; moles fluorocarbon = (Wt. Fluorocarbon fed,grams)/(Mol. Wt.); At. Wt. = atomic weight of halide. Decompositionrates based on chloride analysis for HCFC-122, −225da, and −235fa;fluoride analysis used for all others. ^(g)GC area percentage ofunsaturated product(s) in the recovered fluorinated hydrocarbon.^(h)Maximum value of decomposition rate. For most fluorocarbons, thisassumes one mole of fluorocarbon decomposes to give one mole of fluoride(f = 1). For HFP and HFC-1225zc the maximum value assumes one mole ofthe fluoropropene gives a minimum of two moles of fluoride. ^(i)Minimumvalue of decomposition rate. This assumes that decomposition of one moleof 1225zc, 236fa, or 227ea yields 5, 6, or 6 moles of fluoride,respectively. ^(j)The concentration of unsaturates was about the same asin the starting HFC-365mfc. ^(k)“nd” = not detected

TABLE 2 Alkaline Hydrolysis of Fluorinated Hydrocarbons inCounter-current Scrubbers^(a) Average % % Unsaturate Example FluorideDecomposition in Fluorinated No. Substrate^(b) Scrubbing Media^(c)pH^(d) Level^(e) (ppm) Per Hour^(f) Hydrocarbon^(g) C25 236fa 5% NaOH13.09 1380 0.50 0.066 21 236fa 4% 1:1 K₂HPO₄:K₃PO₄ 11.89 120 0.044 0.03822 236fa 4% 98:2 K₂HPO₄:K₃PO₄ 9.65 1 0.00038 0.017 23 236fa 4% 6:1K₂HPO₄:KH₂PO₄ 7.83 0.5 0.00017 0.019 C26 245fa^(h) 5% NaOH 13.8 1497 8.516.6 24 245fa^(h) 4% 98:2 K₂HPO₄:K₃PO₄ 9.88 11.4 0.062 0.14 25 245fa^(h)4% 6:1 K₂HPO₄:KH₂PO₄ 7.64 4.1 0.016 0.24 ^(a)All reactions wereconducted in a counter-current reactor. The fluorocarbon feed rate was100 sccm and the caustic flow rate was 100 mL/min. The reactions wererun for 3 hours at 60° C. unless indicated otherwise. ^(b)Fluorocarbonfed to scrubber; see Legend. ^(c)Type of aqueous caustic solution usedin counter-current reactor. Percentages are on a weight basis; ratiosare on a molar basis. ^(d)Initial pH of solution of aqueous base in thereservoir. ^(e)Concentration of fluoride in parts per million (weight)in the caustic reservoir at the end of the reaction period. ^(f)AverageRate of Decomposition per Hour = [(Fluoride level)(Wt. Aq.Soln)(100)]/[(f)(moles fluorocarbon)(19)(Time, hours)]where: Fluoridelevel = ppm fluoride/1 × 10⁶; Wt. Aq. Soln = total weight of recoveredcaustic from reservoir; f = stoichiometry factor; f = 6for 236fa and227ea, f = 5 for 1225zc and HFP; f = 1 for 245fa; moles fluorocarbon =(Wt. Fluorocarbon fed)/(Mol. Wt.); 19 = atomic weight of fluorine; Runtime = 3 hours ^(g)GC area percentage of unsaturated product(s) in therecovered fluorinated hydrocarbon ^(h)Run time was 2 hours.

1. A process for reducing the concentration of at least one acidiccontaminant selected from the group consisting of HF, HCl, HBr, HI, HNO₃and H₂SO₄ in a mixture of at least one fluorinated hydrocarbon and saidat least one acidic contaminant comprising: contacting said mixture withat least one phosphorous oxyacid salt, wherein if said salt is inaqueous solution, said aqueous solution has a pH of from about 6 toabout 10, and recovering said at least one fluorinated hydrocarbonhaving reduced concentration of said at least one acidic contaminant,wherein said at least one fluorinated hydrocarbon is selected from thegroup consisting of: (i) unsaturated acyclic fluorinated hydrocarbons ofthe formula C_(n)H_(p)F_(q), wherein n is an integer from 2 to 6, p isan integer from 0 to 11, q is an integer from 1 to 12, and the sum of pand q is equal to 2n, and (ii) unsaturated cyclic fluorinatedhydrocarbons of the formula C_(t)H_(u)F_(v), wherein t is an integerfrom 3 to 6, u is an integer from 0 to 9, v is an integer from 1 to 10,and the sum of u and v is equal to 2t−2.
 2. The process of claim 1wherein said at least one acidic contaminant is selected from the groupconsisting of HF and HCl.
 3. The process of claim 1 wherein said atleast one phosphorous oxyacid salt is in aqueous solution during saidcontacting.
 4. The process of claim 1 wherein said at least onephosphorous oxyacid salt is selected from the group consisting of: (i)orthophosphoric acid salts of the formula M_(n)H_(3-m)PO₄, wherein n isan integer from 1to 3; (ii) phosphorous acid salts of the formulaM_(m)H_(2-m)(HPO₃), wherein m is 1 or 2; (iii) metaphosphoric acid saltsof the formula (MPO₃)_(z), wherein z is an integer from 1 to 6; and (iv)pyrophosphoric acid salts of the formula M_(k)H_(4-k)P₂O₇, wherein k isan integer from 1 to 4, wherein M is selected from the group consistingof NH₄, Li, Na, and K.
 5. The process of claim 4 wherein said at leastone phosphorous oxyacid salt is an orthophosphoric acid salt of theformula M_(n)H_(3-n)PO₄, wherein n is an integer from 1 to 3, and M isselected from the group consisting of NH₄, Na, and K.
 6. The process ofclaim 1 whereby less than about 5 weight percent of said at least onefluorinated hydrocarbon is decomposed by dehydrohalogenation orhydrolysis during said contacting step.
 7. The process of claim 1wherein said mixture is azeotropic or azeotrope-like.
 8. The process ofclaim 1, wherein said at least one fluorinated hydrocarbon obtained fromsaid contacting step contains 10 ppm-molar or less of said at least oneacidic contaminant.
 9. The process of claim 1 wherein said at least onefluorinated hydrocarbon is selected from the group consisting of:tetrafluoroethylene (CF₂═CF₂, TFE), hexafluoropropene (CF₃CF═CF₂, HFP),1,1,3,3,3-pentafluoro-1-propene (CF₃CH═CF₂, HFC-1225zc),1,1,2,3,3-pentafluoro-1-propene (CHF₂CF═CF₂, HFC-1225yc), andhexafluorocyclobutene (cyclo-C₄F₆).
 10. The process of claim 1 whereinsaid mixture contains: mixtures of HFC-227ea and HFP, mixtures ofHFC-236fa and HFC-1225zc, mixtures of HFC-236ea and HFC-1225ye, mixturesof HFC-245fa and HFC-1234ze (CF₃CH═CHF), mixtures of HFC-227ea,HFC-236fa, HFP, and HFC-1225zc, mixtures of HFC-227ea, HFC-245fa, HFP,and HFC-1234ze, or mixtures of HFC-236fa, HFC-245fa, HFC-1234ze, andHFC-1225zc.
 11. The process of claim 1 wherein said at least onefluorinated hydrocarbon has pK₉ value in the range of from about 11 toabout
 25. 12. The process of claim 1 wherein said aqueous solution has apH of from about 6 to about
 8. 13. The process of claim 1 whereby lessthan about 0.5 weight percent of said unsaturated fluorinatedhydrocarbon is decomposed by hydrolysis during said contacting step.